Greenhouse Gases (GHGs)
Climate change science builds on a very simple hypothesis. Anthropogenic (human caused) emissions of greenhouse gasses (GHGs) contribute a layer of gasses around earth's atmoshpere. The accumulation of GHGs then blocks some of earth's emanating heat from escaping to space, causing a general heating or global warming pattern.
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- carbon dioxide (CO2)
- methane (CH4)
- nitrous oxide (N2O)
- hydroflurocarbons (HFCs)
- perflourocarbons (PFCs)
- sulphur hexaflouride (SF6)
Scientists working on climate change research face both theoretical and technical challenges. Theoretically, anthropogenic theories of climate change were matched by theories of natural climate change. One commonly discussed theory falling in the nature induced school of climate change hypothesizes that volcanic eruptions and their effects on atmospheric conditions better accounts for climate variability.
From a technical point of view, scientists working on climate modeling face data problems. Standardized data sets measuring global GHG emissions are the first step in climate modeling following theory. Emissions data sets include information not only on aggregate emissions data but also on the relative power of the various gases to act as atmospheric road blocks.
Scientists call this road blocking ability the Global Warming Potential (GWP) of a gas. The standard measurement unit is 1 for Carbon, and it turns out Carbon is the least effective of the GHGs in trapping earth's heat. For comparative purposes, over a twenty year time span, Methane's GWP=56, Nitrorus Oxide's GWP= 310. The GWP of the engineered chemicals varies from 460-16,000. By far, in terms of climate change power, the engineered chemicals are the most climate warming inducing. (GWP measurement in not extremely accurate. Scientists estimate the margin of error to be +/- 35).
Each GHG also has a life span, or time it remains stable in the atmosphere. Whereas the numbers for carbon look somewhat benign in terms of its GWP, they start to look a bit more daunting when considered in terms of life span. Scientists estimate that CO2 remains stable in the atmosphere for anywhere from 50-200 years. Methane, on the other hand, remains stable only about 12 years. Nitrous Oxide's life span reaches the 120 year mark. Finally the engineered chemicals may remain stable for anywhere from 2 to 50,000 years.
© 2000. Patricia A. Michaels